U.S. patent number 11,000,991 [Application Number 16/008,279] was granted by the patent office on 2021-05-11 for systems and method for four-dimensional printing of elastomer-derived ceramic structures by compressive buckling-induced method.
This patent grant is currently assigned to City University of Hong Kong. The grantee listed for this patent is City University of Hong Kong. Invention is credited to Guo Liu, Jian Lu, Yan Zhao.
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United States Patent |
11,000,991 |
Lu , et al. |
May 11, 2021 |
Systems and method for four-dimensional printing of
elastomer-derived ceramic structures by compressive
buckling-induced method
Abstract
Systems and method of constructing a 4D-printed ceramic object,
the method including extruding inks including particles and
polymeric ceramic precursors through a nozzle to deposit the inks
to form a first elastic structure and a second elastic structure,
subjecting the first elastic structure to a tensile stress along at
least one axis, attaching the second elastic structure to the first
elastic structure, releasing the application of the tensile stress
from the first elastic structure to allow the first elastic
structure and second elastic structure to form a 4D-printed
elastomeric object, and converting the 4D-printed elastomeric
object into the 4D-printed ceramic object.
Inventors: |
Lu; Jian (Kowloon,
HK), Liu; Guo (Kowloon, HK), Zhao; Yan
(Kowloon, HK) |
Applicant: |
Name |
City |
State |
Country |
Type |
City University of Hong Kong |
Kowloon |
N/A |
HK |
|
|
Assignee: |
City University of Hong Kong
(Kowloon, HK)
|
Family
ID: |
68838633 |
Appl.
No.: |
16/008,279 |
Filed: |
June 14, 2018 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20190381725 A1 |
Dec 19, 2019 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C04B
35/565 (20130101); C04B 35/22 (20130101); C04B
35/5603 (20130101); C04B 35/453 (20130101); C04B
35/581 (20130101); C04B 35/528 (20130101); C04B
35/053 (20130101); C04B 35/111 (20130101); C04B
35/522 (20130101); C04B 35/46 (20130101); B29C
64/124 (20170801); C04B 35/01 (20130101); C04B
35/486 (20130101); B29C 64/295 (20170801); B29C
61/08 (20130101); B33Y 30/00 (20141201); B29C
64/112 (20170801); C04B 38/0006 (20130101); C04B
35/14 (20130101); B29C 64/209 (20170801); C04B
38/0006 (20130101); C04B 35/01 (20130101); B33Y
10/00 (20141201); C04B 2235/6581 (20130101); C04B
2111/00181 (20130101); C04B 2235/6026 (20130101); C04B
2235/95 (20130101); C04B 2235/9615 (20130101); C04B
2235/5454 (20130101); B29K 2083/00 (20130101); B29K
2105/162 (20130101); C04B 2235/96 (20130101); B29C
61/065 (20130101) |
Current International
Class: |
B29C
64/124 (20170101); B29C 61/08 (20060101); B29C
64/209 (20170101); B29C 64/112 (20170101); B29C
64/295 (20170101); B33Y 10/00 (20150101) |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Liu et al., Origami and 4D printing of elastomer-derived ceramic
structures, Science Advances, 4 (8), 10.1126/sciadv.aat0641 (Year:
2018). cited by examiner.
|
Primary Examiner: Daniels; Matthew J
Assistant Examiner: Spiel; Paul
Attorney, Agent or Firm: Renner Kenner Greive Bobak Taylor
& Weber
Claims
The invention claimed is:
1. A method of constructing a 4D-printed ceramic object, the method
comprising the steps of: extruding inks including particles and
polymeric ceramic precursors through a nozzle to deposit the inks
to form a first elastic structure and a second elastic structure,
subjecting the first elastic structure to a tensile stress along at
least one axis, extruding joins to attach the second elastic
structure to the first elastic structure, releasing the application
of the tensile stress from the first elastic structure to allow the
first elastic structure and second elastic structure to form a
4D-printed elastomeric object, and converting the 4D-printed
elastomeric object into the 4D-printed ceramic object.
2. A method of constructing a 4D-printed ceramic object in
accordance with claim 1, wherein the second elastic structure
includes at least one area of lower bending stiffness or uniform
bending stiffness.
3. A method of constructing a 4D-printed ceramic object in
accordance with claim 2, wherein the release of the first elastic
structure from the tensile stress further includes the generation
of a relative compressive stress to the second elastic structure
which deforms the second elastic structure.
4. A method of constructing a 4D-printed ceramic object in
accordance with claim 2, wherein the one or more of areas of
reduced bending stiffness are arranged in a buckling pattern.
5. A method of constructing a 4D-printed ceramic object in
accordance with claim 4, wherein the buckling pattern is arranged
in a Miura-ori pattern.
6. A method of constructing a 4D-printed ceramic object in
accordance with claim 1, wherein the first elastic structure is a
planar substrate.
7. A method of constructing a 4D-printed ceramic object in
accordance with claim 1, wherein the tensile stress is provided by
attaching the first elastic structure to a stretching means.
8. A method of constructing a 4D-printed ceramic object in
accordance with claim 7, wherein the stretching means is a biaxial
stretching device.
9. A method of constructing a 4D-printed ceramic object in
accordance with claim 1, wherein at least one of the first elastic
structure and the second elastic structure have a stretch ratio of
3.
10. A method of constructing a 4D-printed ceramic object in
accordance with claim 1, wherein the particles are zirconium
dioxide nanoparticles.
11. A method of constructing a 4D-printed ceramic object in
accordance with claim 1, wherein the polymeric ceramic precursors
are polysiloxanes.
12. A method of constructing a 4D-printed ceramic object in
accordance with claim 11, wherein the polysiloxanes is
poly(dimethylsiloxane).
13. A method of constructing a 4D-printed ceramic object in
accordance with claim 1, wherein the inks are formed from a
homogenous distribution of the particles in the polymeric ceramic
precursors and wherein the weight percentage of the particles in
the inks is in the range of from about 1% to about 90% and the
weight percentage of the polymeric ceramic precursors in the inks
is in the range of from about 10% to about 99%.
14. A method of constructing a 4D-printed ceramic object in
accordance with claim 1, wherein the step of converting the
4D-printed elastomeric object into the 4D-printed ceramic object
further includes heat treatment of the 4D-printed elastomeric
object in a vacuum or under an inert atmosphere.
15. A method of constructing a 4D-printed ceramic object in
accordance with claim 14, wherein the inert atmosphere includes
argon.
16. A method of constructing a 4D-printed ceramic object in
accordance with claim 14, wherein the heating treatment occurs in a
temperature range of 400.degree. C. to 2000.degree. C.
17. A method of constructing a 4D-printed ceramic object in
accordance with claim 1, wherein the step of converting the
4D-printed elastomeric object into the 4D-printed ceramic object
further includes subjecting the 4D-printed elastomeric object to
further heat treatment in air after heat treatment in a vacuum or
under an inert atmosphere.
Description
FIELD OF INVENTION
The present invention relates to the fabrication of ceramic
structures. In particular, embodiments of the invention are
directed to the printing of ceramic structures using
elastomer-derived compounds. Particular embodiments of the ceramic
structures are printed in a manner such that the shape of the
structure is morphed by subjecting the structure to mechanical
forces, temperature variation and chemical processing.
BACKGROUND
In the present specification, it will be understood that the term
"origami" refers to the process of folding thin sheets into
Three-Dimensional (3D) objects. In the context of manufacturing and
3D printing, reference to "origami" assembly, is reference to the
process of causing a 3D-printed object to "fold" or morph into a
more complex shape.
Such folding may occur through the application of capillary force,
by use of a mechanical inductor, or frontal photopolymerization, or
by a shape memory mechanism inherent to the material from which the
3D-printed object is formed.
In colloquial language, 4D printed objects (i.e. objects that are
able to move or transform over time by virtue of their inherent
construction and/or use of materials) are generally fabricated by a
process known as Four-Dimensional (4D) printing. Thus, in the
context of the present specification, it will be understood that
any reference to a "4D printed object" is a reference to an object
that has been printed using a 3D printing technology, but that is
able to transform over time due to inherent properties of the
object. Correspondingly, 4D printing refers to a printing process
whereby a 3D printing mechanism or methodology is employed, and in
some instances, followed by a shape-morphing step, in a manner such
that a 4D-printed object is produced.
As will be appreciated, 4D-printed objects and 4D printing
technology may find application in a number fields including
robotics, life science applications, and biomimetic 4D
printing.
Polymer-Derived Ceramics (PDCs) are a type of ceramic, which are
prepared through thermolysis and chemical treatment of polymeric
ceramic precursors. PDCs exhibit remarkable properties of
conventional ceramics such as high thermal stability, chemical
resistance to oxidation and corrosion, in addition to mechanical
resistance to tribology. The microstructures and properties of PDCs
can be tuned through tailored polymer systems and thermolysis
conditions.
The additive manufacturing of ceramic precursors is a
state-of-the-art technology used to construct complicated ceramic
architectures. However, existing ceramic precursors are not
flexible and sufficiently stretchable to enable self-shaping
assembly prior to polymer-to-ceramic transformation.
It is against this background that the present invention has been
developed.
SUMMARY OF THE INVENTION
In one aspect, the present invention is directed to a method of
constructing a 4D-printed ceramic object, the method comprising the
steps of: extruding inks including particles and polymeric ceramic
precursors through a nozzle to deposit the inks to form a first
elastic structure and a second elastic structure, subjecting the
first elastic structure to a tensile stress along at least one
axis, attaching the second elastic structure to the first elastic
structure, releasing the application of the tensile stress from the
first elastic structure to allow the first elastic structure and
second elastic structure to form a 4D-printed elastomeric object,
and converting the 4D-printed elastomeric object into the
4D-printed ceramic object.
In one embodiment, the second elastic structure includes at least
one area of lower bending stiffness or uniform bending
stiffness.
The release of the first elastic structure from the tensile stress
further includes the generation of a relative compressive stress to
the second elastic structure which deforms the second elastic
structure.
In one embodiment, the one or more of areas of reduced bending
stiffness are arranged in a buckling pattern.
The buckling pattern is arranged in a Miura-ori pattern.
The first elastic structure is a planar substrate.
In one embodiment, the tensile stress is provided by attaching the
first elastic structure to a stretching means.
The stretching means is a biaxial stretching device.
In one embodiment, at least one of the first elastic structure and
the second elastic structure have a stretch ratio of 3.
In one embodiment, the particles are zirconium dioxide
nanoparticles.
In one embodiment, the polymeric ceramic precursors are
polysiloxanes.
In one embodiment, the polysiloxanes is poly(dimethylsiloxane).
In one embodiment, the inks are formed from a homogenous
distribution of the particles in the polymeric ceramic precursors
and wherein the weight percentage of the particles in the inks is
in the range of from about 1% to about 90% and the weight
percentage of the polymeric ceramic precursors in the inks is in
the range of from about 10% to about 99%.
In one embodiment, the converting the 4D-printed elastomeric object
into the 4D-printed ceramic object further includes heat treatment
the 4D-printed elastomeric object in a vacuum or under an inert
atmosphere.
In one embodiment, the inert atmosphere includes argon.
In one embodiment, the heating treatment occurs in a temperature
range of 400.degree. C. to 2000.degree. C.
In one embodiment, the converting the 4D-printed elastomeric object
into the 4D-printed ceramic object further includes subjecting the
4D-printed elastomeric object to further heat treatment in air
after heat treatment in a vacuum or under an inert atmosphere.
In one aspect, the present invention is directed to a system for
constructing a 4D-printed ceramic object comprising: extruding inks
including particles and polymeric ceramic precursors through a
nozzle to deposit the inks to form a first elastic structure and a
second elastic structure, subjecting the first elastic structure to
a tensile stress along at least one axis, attaching the second
elastic structure to the first elastic structure, releasing the
application of tensile stress from the first elastic structure to
allow the first elastic structure and second elastic structure to
form a 4D-printed elastomeric object, and converting the 4D-printed
elastomeric object into the 4D-printed ceramic object.
BRIEF DESCRIPTION OF THE DRAWINGS
Notwithstanding any other forms which may fall within the scope of
the present invention, a preferred embodiment will now be
described, by way of example only, with reference to the
accompanying drawings in which:
FIG. 1 illustrates the compressive buckling-induced origami method
in accordance with an embodiment of the invention.
FIG. 2 illustrates the deformation of a ceramic precursor under
tensile stress with reference to scale bars of 1 cm in accordance
with an embodiment of the invention.
FIG. 3 illustrates the effect of heat treating the ceramic
precursor with reference to scale bars of 1 cm in accordance with
an embodiment of the present invention.
FIG. 4 illustrates the effect of oxidation on the ceramic precursor
with reference to scale bars of 1 cm in accordance with an
embodiment of the present invention.
FIG. 5 illustrates a schematic of a Miura-ori pattern in accordance
with an embodiment of the present invention.
FIG. 6 illustrates a stretch device in accordance with an
embodiment of the present invention.
FIG. 7 illustrates the stages of compressive buckling-induced
ceramic origami for a 4D-printed ceramic object with the Miura-ori
pattern with reference to scale bars of 1 cm in accordance with an
embodiment of the present invention.
FIG. 8 illustrates the process of forming a 4D-printed elastomeric
object with the Miura-ori pattern in accordance with an embodiment
of the present invention.
FIG. 9 illustrates a phase diagram of an FEA simulation of the
variations of the Miura-ori pattern in accordance with an
embodiment of the present invention.
FIG. 10A illustrates a phase diagram of an experimental result of
the variations of the Miura-ori pattern formed by elastomers in
accordance with an embodiment of the present invention.
FIG. 10B illustrates a phase diagram of an experimental result of
the variations of the Miura-ori pattern formed by elastomer-derived
ceramics in accordance with an embodiment of the present
invention.
FIG. 11 illustrates compressive strength-density Ashby Chart
showing the relative compressive strength of the precursor material
in accordance with an embodiment of the present invention.
FIG. 12 illustrates strength-scalability synergy of the precursor
material in accordance with an embodiment of the present
invention.
FIG. 13A, FIG. 13B, FIG. 13C, FIG. 13D and FIG. 13E are
illustrations of example geometric representations of the
associated entries in Table 1.
FIG. 14 is an illustration of an example geometric representation
of the associated entries in Table 2.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In the ensuing description, certain terms, once introduced, will be
abbreviated for the sake of brevity and to improve readability. It
will be understood that the use of such abbreviations should not be
construed as being limiting or otherwise placing a "gloss" on the
meanings of such terms beyond the meanings that would be placed on
the terms when construed by a skilled addressee.
Broadly, one of the inventive aspects is directed to a method of
constructing a 4D-printed ceramic object, the method comprising the
following steps. Firstly, extruding inks including particles and
polymeric ceramic precursors through a nozzle to deposit the inks
to form a first elastic structure and a second elastic structure.
The first elastic structure is subjected to a tensile stress along
at least one axis. The second elastic structure is attached to the
first elastic structure, after which the tensile stress applied to
the first elastic structure is released to allow the first elastic
structure and second elastic structure to form a 4D-printed
elastomeric object. The 4D-printed elastomeric object is converted
into the 4D-printed ceramic object.
In another aspect, the invention is directed to a system for
constructing a 4D-printed ceramic object comprising: extruding inks
including particles and polymeric ceramic precursors through a
nozzle to deposit the inks to form a first elastic structure and a
second elastic structure, subjecting the first elastic structure to
tensile stress along at least one axis, attaching the second
elastic structure to the first elastic structure, releasing the
application of tensile stress from the first elastic structure to
allow the first elastic structure and second elastic structure to
form a 4D-printed elastomeric object, and converting the 4D-printed
elastomeric object into the 4D-printed ceramic object.
Specific embodiments will now be described in more detail with
reference to the drawings. In an embodiment, a known and cost
efficient 4D printing method is used to form the 4D ceramic
structure. One such method may include Direct Ink Writing (DIW) to
form a first elastic structure and a second elastic structure from
the ceramic precursor. However, other forms of additive
manufacturing techniques such as fused filament fabrication (FFF),
Rapid Liquid Printing (RLP), Aerosol Jet, and Fluidic force
microscopy (FluidFM) techniques may also be used to form the 4D
ceramic structure as would be understood by the person skilled in
the art.
Polydimethylsiloxane (PDMS) is a dominant elastomer in silicone
systems and is useful as a ceramic precursor, while providing
inherent flexibility to construct a material that is suitable for
subjecting to tensile stress without the material experiencing
plastic deformation. Furthermore, the stretchability of PDMS allows
for the creation of complex structures. However, it will be
understood that the polymeric ceramic precursors may also include
polysiloxanes, polysilsesquioxanes, polycarbosiloxanes,
polycarbosilanes, polysilylcarbodiimides,
polysilsesquicarbodiimides, polysilazanes, polysilsesquiazanes or
any combination of the above
In an embodiment, the inks are formed from a homogenous
distribution of the particles in the elastomeric ceramic precursor
material. For example, the weight percentage of the particles in
the inks is in the range of from about 1% to about 90% and the
weight percentage of the polymeric ceramic precursors in the inks
is in the range of from about 10% to about 99%.
In the example given with reference to the Figures, crystalline
ZrO.sub.2 (Zirconium dioxide) nanoparticles with a primary average
size of 20-50 nm in diameter were incorporated into a PDMS matrix,
forming a jammed network within the polymer matrix while serving as
barriers to mass and heat transfer in the polymer matrix, to
thereby eliminate shrinkage upon ceramization.
It will be understood that the nanoparticles may also include other
variants, such as but not limited to, calcium oxide particles,
aluminium oxide particles, titanium dioxide particles, indium oxide
particles, zinc oxide particles, silicon dioxide particles,
aluminium nitride particles, calcium silicate particles, silicon
carbide particles, polymeric particles, metallic particles, carbon
black particles, graphene particles, graphite particles, diamond
particles, other refractory materials or any combination of the
particles listed above. The particles, in the embodiment, are
characterized by an average diameter of about 100 .mu.m or less and
may be uniformly or non-uniformly distributed powders or fibres or
tubes or any other regular shapes or any other combination of the
above.
Referring to FIG. 1, an embodiment includes a DIW apparatus 100
which is used to fabricate one or more 4D elastomeric structures. A
first elastic structure may be in the form of an elastic substrate
102. In an embodiment, the elastic substrate is in the form of a
lattice of perpendicular strips of elastic ceramic precursor.
Alternatively, the elastic substrate may be formed in a honeycomb
pattern of interconnecting polygons or as a solid piece of elastic
ceramic precursor. Moreover, the elastic substrate 102 may be
formed by the gradual accumulation or deposition of one or more
layers of elastic ceramic precursor.
The elastic substrate is subjected to tensile pressure along at
least one axis 104. In an embodiment, the elastic substrate is
subjected to tensile stress along the x-axis as shown in FIG. 1.
This may be achieved by a stretching means, such as but not limited
to, a uni-lateral stretching device. However, as would be
understood by the person skilled in the art, the substrate may be
subjected to tensile stress along any number of axes, and as such,
the stretching device would be designed or modified in order to
provide suitable tensile stress along those axes. For example, a
stretching means may also include a bi-axial or multi-axial
stretching device.
In an embodiment, the DIW apparatus 100 is also be used to
fabricate a second elastic structure. The second elastic structure
may be in the form of a ceramic precursor 106 formed from one or
more layers of elastic ceramic precursor. The ceramic precursor 106
may also include one or more creases or areas of lower bending
stiffness relative to other area of the ceramic precursor 106 or
one or more creases or areas of uniform bending stiffness. The
ceramic precursor 106 may also include areas of relatively fewer
layers, such that the ceramic precursor may include areas of
relatively reduced thickness and bending stiffness. The ceramic
precursor 106 may be shaped to form a Miura-ori pattern, lattice,
strip or any other suitable shape of elastic ceramic precursor
material to form the desired 4D elastomeric object.
The ceramic precursor 106 is attached to the elastic substrate,
while the elastic substrate is subjected to tensile stress. The
ceramic precursor 106 is attached to the elastic substrate by one
or more joins. In an embodiment, the one or more joins are printed
or fabricated on to the elastic substrate by a DIW apparatus 100.
The one or more joins are provided to the elastic substrate at
buckling critical locations in accordance with the desired shape of
the 4D elastomeric object. For example, in FIG. 1, the one or more
joins 112 are provided to the boundary of the shape along the axis
of tensile stress. The one or more joins 112 may be cuboid,
cylindrical or any other suitable shape that provides sufficient
contact between the elastic substrate, the one or more joins, and
the ceramic precursor. In an embodiment, once the ceramic precursor
is in connection with the elastic substrate via the one or more
joins, heat is applied to enable the joins to connect the ceramic
precursor and elastic substrate together at 114. Heat may be
applied to the ceramic precursor, elastic substrate and the one or
more joins by means of an oven, heating plate or pin point
application.
For instance, the joints may be also made of printable inks, which
share the same printable inks with the two elastic structures 106
and 110. Upon heating the joints at a predetermined temperature
e.g. 150.degree. C. for 30 mins, the liquid joints i.e. inks are
solidified. Hence, the joints may connect the two elastic
structures even after the releasing of the prestrains.
Once the ceramic precursor and elastic substrate have been joined
together, the tensile stress subjected to the elastic substrate is
released. Due to the elastomeric properties of the elastic
substrate, returns to its original dimensions. Due to the high
stretch ratio of the ceramic precursor, the substrate does not
experience plastic deformation. The release of the elastic
substrate releases the elastic potential energy stored in the
pre-stretched structure. However, as the ceramic precursor is now
joined to the elastic substrate, the elastic potential energy is
transferred to the ceramic precursor. The ceramic precursor is
subjected to compressive stress as the elastic substrate returns to
its original dimensions. As a result, the ceramic precursor
buckles, folds or deforms in the areas of reduced bending stiffness
116 within the pattern which forms a 4D elastomeric object.
In accordance with the broader concept and the embodiments
described and defined herein, the 4D elastomeric object may be
transformed into a 4D ceramic object. The elastomer-to-ceramic
transformation may include the application of pyrolysis in inert
atmosphere, oxidation in oxidative atmosphere or a combination of
the techniques.
In an embodiment, the 4D elastomeric object is first subjected to
pyrolysis in inert atmosphere to produce a first elastomer derived
ceramic (EDC) object 118. The inert atmosphere may include argon
gas or another inert gas. Alternatively, the 4D elastomeric object
is subjected to heating in contained area containing a vacuum.
Heating of the 4D elastomeric object may occur between 400.degree.
C. to 2000.degree. C. The first EDC object 118 is then subjected to
oxidation by heat treatment such as heating the first EDC object in
1000.degree. C. in an oxygen rich atmosphere e.g. in air to produce
a second EDC object 120. The combination of both steps provides a
relative increase in density when comparing the first EDC object
118 to the second EDC object 120. Furthermore, the combination of
both techniques enables the resulting 4D ceramic object to be
formed in different colours.
Referring to FIG. 2, a stretching apparatus 200 is provided at
different stages. A first stage 202 includes an elongated portion
of a first elastic structure 204 within a uni-axial stretching
device 206. The uni-axial stretching device 206 includes a pair of
clamps 208, which retain the distal ends of the first elastic
structure 204. The first elastic structure is stretched at 210 and
deformed.
In a second stage 212, the elongated portion of a first elastic
structure 214 is deformed within a uni-axial stretching device 216
between clamps 218. By way of example only, the first elastic
structure 214 is deformed to twice its original length as measured
by a stretch ratio of 3 i.e. beyond 3 times its original length, or
a 200% increase in length due to deformation. However, the first
elastic structure 214 may be deformed up to an including three or
four times its original length and as such may have a stretch ratio
of three or four respectively. The tensile stress is then released
at 220.
In a third stage 222, the elongated portion of a first elastic
structure 224 has been released from the tensile stress by the
uni-axial stretching device 216 having the clamps 218 move towards
one another. This results in the elongated portion of a first
elastic structure 224 having an approximate residual stretch ratio
of 0.1.
In an embodiment, the weight percentage of the nanoparticles in the
inks is in the range of from about 1% to about 90% and the weight
percentage of the polymeric ceramic precursors in the inks is in
the range of from about 10% to about 99%. For the purposes of
demonstrating the workings of the invention, an example is provided
that includes inks with two different weight percentages of
nanoparticles. In a first ink mixture, the ceramic precursor of
PDMS includes 20 wt % of zirconium dioxide nanoparticles. In a
second ink mixture, the ceramic precursor of PDMS includes 40 wt %
of zirconium dioxide nanoparticles.
Referring to FIG. 3, a comparison 300 is provided between a first
elastic substrate formed from PDMS 302 and second elastic substrate
formed from PDMS and 40 wt % of zirconium dioxide nanoparticles
304. Each of the elastic substrates 302 and 304 are subjected to
heating in an atmosphere of argon. The first elastic substrate
formed from PDMS 302 is transformed via the heating process into a
first ceramic object 306 which is shown to have poor structural
stability. The second elastic substrate formed from PDMS and 40 wt
% of zirconium dioxide nanoparticles 304 is transformed via the
heating process into a second ceramic substrate 308, which is shown
to have maintained its structure but has exhibited some
shrinkage.
A further comparison 310 is provided between a first elastic
substrate formed from PDMS 312 and second elastic substrate formed
from PDMS and 20 wt % of zirconium dioxide nanoparticles 314. Each
of the elastic substrates 312 and 314 are subjected to heating in
an atmosphere of argon. The first elastic substrate formed from
PDMS 312 is transformed via the heating process into a first
ceramic object 316 which is shown to have experience linear
shrinkage of 27%. The second elastic substrate formed from PDMS and
20 wt % of zirconium dioxide nanoparticles 314 is transformed via
the heating process into a second ceramic substrate 318, which is
shown to experienced 24% shrinkage. The inclusion of zirconium
dioxide nanoparticles at both 20 wt % and 40 wt % improves the
structural stability and reduces the shrinkage of the precursor
material when undergoing ceramization.
Referring to FIG. 4, a comparison is provided between the first ink
mixture 400 formed from PDMS and 40 wt % of zirconium dioxide
nanoparticles and the second ink mixture 410 formed from PDMS and
20 wt % of zirconium dioxide nanoparticles.
The elastic substrate including 40 wt % of zirconium dioxide
nanoparticles 402 is first subjected to heating in an inert
atmosphere to produce a first EDC 404. The first EDC 404 is
subsequently subjected to oxidation to form a second EDC 406.
The first EDC 404 and second EDC 406 show increased structural
integrity compared with a first elastic precursor 408 which was
subjected to oxidation without first being subjected to
heating.
The elastic substrate including 20 wt % of zirconium dioxide
nanoparticles 412 is first subjected to heating in an inert
atmosphere to produce a first EDC 414. The first EDC 414 is
subsequently subjected to oxidation to form a second EDC 416. The
first EDC 414 and second EDC 416 show increased structural
integrity compared with a first elastic precursor 418 which was
subjected to oxidation without first being subjected to
heating.
Referring to FIG. 5, an embodiment is provided that includes a
Miura-ori patterned ceramic precursor and elastic substrate 500.
The elastic substrate 502 is connected to the ceramic precursor 504
by joins 506. The Miura-ori patterned ceramic precursor 504
includes one or more creases 508 which are areas of reduced bending
stiffness. The creases 508 act to define the Miura-ori pattern on
the ceramic precursor. By way of an example only, the ceramic
precursor in a Miura-ori pattern includes the geometric parameters
of l.sub.1=l.sub.2=9 mm, c=1.8 mm, and .alpha.=75.degree., as the
Miura-ori can pattern can serve as an elementary geometric
construction for engineering more complex-shaped origami structures
so to assist the reader to understand the workings of the
invention. As such, it would be understood by the person skilled in
the art that other geometric parameters and patterns may be
used.
For example, a further example of geometric parameters is provided
in the optical images depicted in FIG. 7. An embodiment of the
present invention may include the fabrication of the elastic
substrate including a nine-layer triangular pattern (6 cm.times.6
cm.times.0.3 cm, nozzle diameter 410 .mu.m, center-to-center
ligament spacing 1 mm). The ceramic precursor includes creases of
sufficient depth on the surface in order to provide areas of lower
bending stiffness or uniform bending stiffness. The areas of lower
bending stiffness or uniform bending stiffness enable easy folding
and buckling deformation of the structure. The ceramic precursor
includes a three-layers of ink parallelogram pattern with an
overall height of approximately 0.7 mm. In particular, the
three-layers of ink includes layers of printed ligament, each
thickness of which includes diameter of extruded ligament of about
410 .mu.m. The creases are formed to a depth of one-layer between
the patterns. That is, the creases are areas, or paths of reduced
ceramic precursor thickness. Furthermore, the Miura-ori design may
be filled with square patterns with a center-to-center ligament
spacing of 1 mm. Cuboid joins may also be provided to join the
elastic substrate and ceramic precursor. The joins may have the
dimensions of 3.5 mm.times.0.9 mm.times.0.3 mm, wherein the entire
structure is heated in order to fuse the joints.
The inks are extruded by means of a nozzle provided to the DIW
apparatus (not shown), where the nozzle may be provided with a
variety of different nozzle dimensions. For example, the nozzle
diameter may be 410 .mu.m.
Referring to FIG. 6, an example of a bi-axial stretching device 600
is provided. A square elastic substrate 602 is provided wherein,
each side of the elastic substrate 602 is held by a clamping
portion 604. Each clamping portion 604 is retracted in order to
subject the elastic substrate 602 to tensile stress in both the x
and y axes. The clamps may be retracted by a variety of different
mechanisms. For example, the clamping portions 604 may be connected
to two pairs of stepper motors 606 which provide a fine level of
control over the tensile stress provided to the elastic substrate
602. Furthermore, the stepper motors may be programmable. For
example, during the process of releasing the tensile stress from
the substrate, the releasing speeds of the substrate in x and y
directions may be 4.86 millimetres per second and 2.00 millimetres
per second respectively. Further, a control or displacement
measuring means 608 may also be included in the stretching device
600. Moreover, a base 610 may also be provided to support the
elastic substrate whilst being subjected to tensile stress.
Referring to FIG. 7, a comparison 700 is provided of simulated and
experimental results of fabricating a 4D ceramic object in
accordance with the broader concept and the embodiments described
and defined herein. The elastic substrate 702 and ceramic precursor
704 are fabricated using one of the additive manufacturing methods
described above, such as but not limited to, DIW printing. The
elastic substrate 702 is subjected to tensile stress and connected
to ceramic precursor 704 as previously described to form a 4D
printed ceramic precursor. A Finite Element Analysis (FEA)
simulation was undertaken to determine the expected shape of the 4D
printed ceramic precursor 706. A prototype 4D printed ceramic
precursor 708 was fabricated in accordance with the above described
method, which was subjected to heating to form a first EDC 710 and
subsequently subjected to oxidation to form a second EDC 712. As
can be seen from the figures, the expected shape of the 4D printed
ceramic precursor 706 and the prototype 4D printed ceramic
precursor 708 are very similar to one another.
In one example embodiment of ink system, liquid PDMS (XE15-645,
Momentive Performance Materials) is formulated by mixing PDMS
prepolymer and curing agent at a 1:1 weight ratio. The ink mixture
is manually blended by a glass rod for 30 minutes. 40 wt % (11 vol
%) ZrO.sub.2 NPs is then added. After manually blending or mixing
by the triple rollers mills (EXAKT: 80E) for 2 hours, the ink
mixture is poured into a printing syringe and is degassed for 2
hours at room temperature. Advantageously, the ink is printable for
over 8 hours at room temperature, and its printability could last
for over half a year if stored in a refrigerator at -80.degree. C.
(Thermo Scientific).
In another example embodiment of ink system, liquid PDMS (SE1700
clear) is formulated by mixing PDMS prepolymer and curing agent at
a 10:1 weight ratio. The ink mixture is manually blended by a glass
rod for 30 minutes. 20 wt % ZrO.sub.2 NPs is then added, mixed by
the triple rollers mills (EXAKT: 80E) for 2 hours, and poured into
printing syringe. Afterwards, the ink is centrifuged to remove gas
bubbles.
Referring to FIG. 8, an embodiment is provided which shows a
bi-axial stretching device 800 to provide tensile stress to the
elastic substrate at three stages. At a first stage 802, the
elastic substrate 804 is under tensile stress provided by two pairs
of clamps 806 which are provided along the x-axis and y-axis
boundaries of the elastic substrate. The tensile stress results in
strain i.e. maximum compressive strain of the precursors or the
second elastic structure along the x-axis of 30% and along the
y-axis of 15%. A ceramic precursor 808 shaped to form a Miura-ori
pattern is in connection with a first face of the elastic
substrate. A FEA simulation 810 shows the elastic substrate and
ceramic precursor in further detail. In the first stage 802 the
ceramic precursor experiences no buckling.
A second stage 812 is provided which shows a gradual release of the
tensile stress subjected to the elastic substrate 814. The second
stage 812 includes the clamps 816 extending towards the elastic
substrate 814 resulting in the ceramic precursor 818 starting to
buckle in accordance with the areas of reduced bending stiffness in
the Miura-ori pattern. A FEA simulation 820 shows the buckling of
the ceramic precursor in further detail.
A third stage 822 is provided which shows a further release of the
tensile stress subjected to the elastic substrate 824. The second
stage 822 includes the clamps 826 extending further towards the
elastic substrate 824 resulting in the ceramic precursor 828
experiencing significant buckling in accordance with the areas of
reduced bending stiffness in the Miura-ori pattern. A FEA
simulation 830 shows the buckling of the ceramic precursor in
further detail.
Referring to FIG. 9 for the graph plotting the strain of the
precursor in the y-axis against the strain of the precursor in the
x-axis, a phase diagram 900 is provided which summarises the
results of an FEA simulation conducted in relation to the
hypothesized formation of 4D elastomeric object prior to
ceramization. The phase diagram 900 illustrates series of
complex-shaped ceramics with continuously variable geometries can
be derived from a simple design.
Referring to FIG. 10A for the graph plotting the strain of the
precursor in the y-axis against the strain of the precursor in the
x-axis, a phase diagram 1000 is provided which summarises the
results of elastomeric experimentation conducted in relation to the
hypothesized formation of 4D elastomeric object prior to
ceramization. Referring to FIG. 10B for the graph plotting the
strain of the elastomer-derived ceramics in the y-axis against the
strain of the elastomer-derived ceramics in the x-axis, a phase
diagram 1100 is provided which summarises the results of
elastomeric experimentation conducted in relation to the
hypothesized formation of 4D ceramic object subsequent to
ceramization. The phase diagram 900 illustrates series of
complex-shaped ceramics with continuously variable geometries can
be derived from a simple design.
To characterize mechanical robustness of these ceramic
architectures, compression tests were performed on printed ceramic
lattices and honeycombs, both for first and second EDCs. The
results of this testing were summarized in FIG. 11, FIG. 12, and
Tables 1 and 2, where Tables 1 and 2 are provided on the following
two pages.
A compressive strength of 547 MPa was achieved on the lattice
structure at 1.6 g cm.sup.-3, and the specific compressive strength
of the tested EDCs was approximately nineteen times as high as
conventional accessible SiOC foam. Ceramic structures as described
and defined in the present invention overcame the
strength-scalability trade-off in traditional printed ceramics,
such as previous works of 3D-printed SiOC microstructures and
ceramic/ceramic composite nanostructures constructed by 3D laser
lithography and atomic layer deposition as shown in FIG. 12.
Furthermore, unlike current use of 3D laser lithography, the
present invention provided a means to fabricate large-scale ceramic
architectures overcoming the challenge of scalability.
Therefore, the broad concept and the embodiments described and
defined herein provide both light and strong hierarchical ceramic
structures have great potential for the fabrication of multiscale
mechanical metamaterials.
TABLE-US-00001 TABLE 1 Compression test samples with various
conditions. Mximum temperature Atmo- Dimen- in heat sphere sions
Mass Dimen- treatment in heat of the of the sions Mass Den-
Compres- for 1.sup.st treatment pre- pre- of the of the sity sive
EDCs for 1.sup.st Architec- Geo- d a b cursor* cursor sample sample
(g strength Ink Material (.degree. C.) EDCs ture metry (.mu.m) (mm)
(mm) (mm) (g) (mm) (g) cm.sup.-3) (MPa) System 1 1.sup.st 1000
Vacuum Lattice See 208 0.64 0.64 10.40 .times. 0.162 8.40 .times.
0.108 1.18 205.8 EDCs FIG. 10.38 .times. 8.40 .times. 13A 1.59 1.30
System 1 1.sup.st 1000 Vacuum Lattice 208 0.64 0.64 10.32 .times.
0.151 8.33 .times. 0.099 1.14 160.4 EDCs 10.32 .times. 8.33 .times.
1.52 1.25 System 1 1.sup.st 1000 Vacuum Lattice 208 0.64 0.64 10.50
.times. 0.136 8.44 .times. 0.089 1.04 150.2 EDCs 10.50 .times. 8.42
.times. 1.54 1.21 System 1 1.sup.st 1000 Argon Lattice 208 0.64
0.64 10.72 .times. 0.173 8.62 .times. 0.112 1.16 207.0 EDCs 10.61
.times. 8.52 .times. 1.60 1.31 System 1 1.sup.st 1000 Argon Lattice
208 0.64 0.64 10.72 .times. 0.155 8.57 .times. 0.100 1.14 211.2
EDCs 10.59 .times. 8.49 .times. 1.51 1.21 System 1 1.sup.st 1000
Argon Lattice 208 0.64 0.64 10.70 .times. 0.148 8.62 .times. 0.094
1.08 174.0 EDCs 10.58 .times. 8.42 .times. 1.46 1.20 System 1
1.sup.st 1000 Argon Honey- See 208 2.25 1.30 11.02 .times. 0.086
0.96 .times. 0.057 0.49 34.2 EDCs comb FIG. 10.25 .times. 8.30
.times. 13B 1.93 1.55 System 1 1.sup.st 1000 Argon Honey- 208 2.25
1.30 11.06 .times. 0.088 8.85 .times. 0.057 0.57 53.9 EDCs comb
10.21 .times. 8.28 .times. 1.66 1.36 System 1 1.sup.st 1000 Argon
Honey- 208 2.25 1.30 11.20 .times. 0.080 8.98 .times. 0.052 0.54
58.6 EDCs comb 10.49 .times. 8.54 .times. 1.58 1.25 System 1
1.sup.st 1000 Argon Honey- 208 2.25 1.30 10.95 .times. 0.135 8.90
.times. 0.087 0.64 41.6 EDCs comb 10.29 .times. 8.39 .times. 2.30
1.83 System 1 1.sup.st 1000 Argon Honey- 208 2.25 1.30 11.13
.times. 0.116 8.92 .times. 0.075 0.62 46.8 EDCs comb 10.02 .times.
8.10 .times. 2.12 1.68 System 1 1.sup.st 1000 Argon Honey- 208 2.25
1.30 10.86 .times. 0.145 8.74 .times. 0.095 0.69 42.9 EDCs comb
10.07 .times. 8.18 .times. 2.38 1.93 System 1 2.sup.nd 1000 Vacuum
Lattice See 203 0.63 0.63 8.25 .times. 0.095 8.01 .times. 0.092
1.19 172.2 EDCs FIG. 8.25 .times. 8.01 .times. 13C 1.26 1.21 System
1 2.sup.nd 1000 Vacuum Lattice 203 0.63 0.63 8.40 .times. 0.093
8.11 .times. 0.090 1.14 150.7 EDCs 8.34 .times. 8.24 .times. 1.23
1.18 System 1 2.sup.nd 1000 Vacuum Lattice 203 0.63 0.63 8.38
.times. 0.097 8.20 .times. 0.095 1.16 175.2 EDCs 8.42 .times. 8.16
.times. 1.27 1.22 System 1 2.sup.nd 1000 Argon Lattice 203 0.63
0.63 8.64 .times. 0.099 8.43 .times. 0.098 1.14 169.3 EDCs 8.51
.times. 8.31 .times. 1.26 1.23 System 1 2.sup.nd 1000 Argon Lattice
203 0.63 0.63 8.59 .times. 0.101 8.40 .times. 0.100 1.18 182.9 EDCs
8.51 .times. 8.30 .times. 1.24 1.22 System 1 2.sup.nd 1000 Argon
Lattice 203 0.63 0.63 8.57 .times. 0.091 8.40 .times. 0.090 1.12
169.2 EDCs 8.53 .times. 8.34 .times. 1.16 1.15 System 1 2.sup.nd
1000 Argon Honey- See 203 2.20 1.27 8.89 .times. 0.056 8.71 .times.
0.054 0.61 74.3 EDCs comb FIG. 8.24 .times. 8.15 .times. 13D 1.29
1.25 System 1 2.sup.nd 1000 Argon Honey- 203 2.20 1.27 9.05 .times.
0.053 8.90 .times. 0.051 0.52 57.7 EDCs comb 8.53 .times. 8.31
.times. 1.35 1.33 System 1 2.sup.nd 1000 Argon Honey- 203 2.20 1.27
9.02 .times. 0.060 8.80 .times. 0.057 0.59 57.3 EDCs comb 8.52
.times. 6.30 .times. 1.34 1.33 System 1 2.sup.nd 1000 Argon Honey-
203 2.20 1.27 8.84 .times. 0.078 8.61 .times. 0.076 0.67 55.9 EDCs
comb 8.14 .times. 7.92 .times. 1.71 1.66 System 1 2.sup.nd 1000
Argon Honey- 203 2.20 1.27 8.84 .times. 0.095 8.56 .times. 0.094
0.79 75.1 EDCs comb 8.36 .times. 8.12 .times. 1.76 1.71 System 1
2.sup.nd 1000 Argon Honey- 203 2.20 1.27 8.88 .times. 0.093 8.60
.times. 0.092 0.76 70.7 EDCs comb 8.31 .times. 8.05 .times. 1.74
1.74 System 2 1.sup.st 1300 Argon Lattice See 198 0.61 0.61 14.46
.times. 2.132 11.04 .times. 1.697 1.26 221.5 EDCs FIG. 14.41
.times. 11.01 .times. 13E 14.54 11.09 System 2 1.sup.st 1300 Argon
Lattice 198 0.61 0.61 14.59 .times. 2.422 11.17 .times. 1.939 1.40
232.6 EDCs 14.57 .times. 11.21 .times. 14.82 11.09 System 2
1.sup.st 1300 Argon Lattice 198 0.61 0.61 14 56 .times. 2.334 11.08
.times. 1.654 1.37 267.1 EDCs 14.53 .times. 11.07 .times. 14.59
11.03 *Precursor; PDMS NCs for 1.sup.st EDCs; 1.sup.st EDCs for
2.sup.nd EDCs
TABLE-US-00002 TABLE 2 Compression test samples in FIG. 4 (Ink
System 1, 1.sup.st EDCs from heat treatment in argon at
1300.degree. C.). Dimensions Mass Specific of the of the
Compressive compressive d a b sample sample Density strength
strength Geometry (.mu.m) (mm) (mm) (mm) (g) (g cm.sup.-3) (MPa)
(MPa cm.sup.3 g.sup.-1) See FIG. 203 0.62 0.62 8.18 .times. 8,13
.times. 1.22 0.124 1.53 333.6 218.0 14 203 0.62 0.62 8.15 .times.
8.10 .times. 1.34 0.121 1.36 301.6 221.0 203 0.62 0.62 8.13 .times.
8.09 .times. 1.31 0 114 1.32 298.4 225.5 203 0.62 0.62 8.13 .times.
8.00 .times. 1.32 0.119 1.38 316.4 229.8 203 0.62 0.62 7.74 .times.
7.71 .times. 1.13 0.117 1.74 453.8 260.8 203 0.62 0.62 8.14 .times.
8.07 .times. 1.34 0.130 1.48 385.9 261.5 203 0.62 0.62 7.90 .times.
7.84 .times. 1.20 0.127 1.70 484.9 285.2 203 0.62 0.62 7.97 .times.
7.78 .times. 1.21 0 122 1.63 474.3 291.0 203 0.62 0.62 7.82 .times.
7.72 .times. 1.20 0 124 1.71 608.2 297.2 203 0.62 0.62 8.06 .times.
7.99 .times. 1.16 0.111 1.49 449.4 301.6 203 0.62 0.62 7.84 .times.
7.83 .times. 1.20 0.120 1.63 496.9 304 8 203 0.62 0.62 8.07 .times.
7.99 .times. 1.21 0.113 1.45 455.8 314.3 203 0.62 0.62 8.11 .times.
7.95 .times. 1.23 0 117 1.48 496.3 335.3 203 0.62 0.62 7.917.90
.times. 1.14 0 116 1.62 646.7 337.4 203 0.62 0.62 8.03 .times. 7.96
.times. 1.20 0.112 1.46 496.7 339.2
ADVANTAGES AND INDUSTRIAL APPLICABILITY
The embodiments and broader invention described herein provide a
number of advantages and have broad industrial applicability.
Firstly, the techniques and materials utilised and developed as
part of the embodiments described herein provide for the creation
of ceramic objects with programmable and customizable designs.
Secondly, advanced shape-morphing systems, inspired by compressive
buckling-induced origami, enable the design of high-resolution
complex ceramics are almost impossible to create by any other
method due the complexity of the high-resolution complex
ceramics.
Moreover, 4D printing of ceramics enable the design higher
resolution than 3D printing. Variation of the self-forming method
parameters provides high-fidelity in geometrical resolution
involved in shape-morphing process, for example, displacement
control in the stretch device.
A further advantage is that DIW-heat treatment method is a
relatively cost effective compared to other additive manufacturing
techniques for ceramics. Once driving factor for the cost
effectiveness of the use of the DIW-heat treatment method is that
it does not require the use of costly high energy apparatus that
are required for other techniques. For example, 3D lithography
techniques require an expensive laser or UV energy apparatuses
other techniques involving the sintering of ceramic powders require
an apparatus that fuses the powders at high temperatures at or
above 1600.degree. C. for ceramic powered compounds such as SiC and
Si.sub.3N.sub.4.
Moreover, shape-morphing capabilities of elastomers improves the
adaptability of structural materials to versatile application
environments. For example, the embodiments of the present invention
provide advantageous applications in space exploration as
3D-printed elastomeric precursors can be folded to save valuable
space prior to launch, and then spread into desired structures at a
later stage in the journey. After elastomer-to-ceramic
transformation, 4D-printed ceramics provide thermal resistant and
mechanically robust structures which is particularly useful for
space craft on re-entry into an atmosphere.
Additionally, the method described demonstrates a
strength-scalability synergy, meaning that the techniques and
materials described herein are highly advantageous for application
in production on an industrial scale.
Further, the techniques and materials utilised and developed as
part of the embodiments are cost effective and enable the
fabrication of 4D printed ceramic structures in a cost-efficient
manner. For example, for a series of complex-shaped ceramics with
similar geometries, the embodiments of the present invention
provide a comparatively cost and time effective means of
fabricating a series of complex-shaped ceramics with continuously
variable geometries that are capable of being derived from a simple
design.
Furthermore, all the materials and techniques used in the
embodiments are based on commercially available and open-end
feedstock systems, which enables the embodiments described herein
to have commercial potential and industrial applicability without
excessive initial capital expenditure on custom fabrication
machinery.
Lastly, in a more general sense, the abovementioned advantages
provide enable the materials and techniques of the embodiments to
be utilized in many structural applications including autonomous
morphing ceramic composites, aerospace propulsion components, and
high temperature microelectromechanical systems.
* * * * *